Homebrew 3CX3000A7 Amplifier

Note: I have many images of the build in progress- It will take some time for me to get this page into shape=

I had been looking for a rugged HF linear amplifier with plenty of headroom. I had a Yeasu 2100F, Heathkit Warrior, and Henry 2K3. I just wasn’t getting the dynamic range out of these amps. Here’s my build along the way. It’s still not complete but is on the air. I ordered a complete set of control and instrumentation boards from WD7S- all the boards are now completed, hope finish the amp in a month or two.

I started with a prototype. It was built inside an old HP server. I realized I didn’t need the sides as much as a plenum underneath. This is a working amp- the odd blue form is a welding rod container wrapped with 6 ga wire. It’s my first filament choke.

After some success with a prototype I bought some stock- 60′ of 1 1/4″ angle iron, a 4′ x 8′ sheet of 16 ga sheet metal and one of aluminum.

It took far longer to fabricate the frame than I had figured on.

Here it is with skins.

First layout RF deck-

Second layout RF deck- stacked cap give more room for the magnetic fields crated by the roller inductors.

Filament choke

Using the amplifier’s frame to bend the aluminum plenum

Plenum

Plate choke is off the shelf similar to Ameritron’s

Tube socket is from a Continental 317C. I’ve relieved the sides to increase air flow

Building the Pi input board from WD7S. The enameled wire is not included- I stripped some from transformers

Input Pi finished and mounted under 3CX3000A7. It’s an ideal location- air cooled and connected with only the capacitor’s leads

3CX3000 center tapped filament transformer from a Continental 317C. It was designed for this tube- though an A1 as an audio modulator.